The population of older persons in the US is rapidly increasing with more than 17 percent of the population expected to be over age 65 by the year 2010. Maintenance of good health, independence and a high quality of life is a major goal for these individuals as well as a public health priority. Participation in "Western Exercise" programs has been shown to maintain or increase muscular strength and endurance and cardiorespiratory capacity in older persons. While in use in Asia for more than two thousand years by many older persons, little scientific data exist on the health and performance benefits of Tai Chi exercise. Tai Chi is a low impact exercise that can be performed by most ambulatory older people and preliminary research has demonstrated that it may decrease falls by increasing balance and other measures of physical performance. Also, there are many claims but little data on the stress reduction benefits and "feeling of well being" achieved by participants of Tai Chi. The major objective of this study is to evaluate the effects of a one year program of "Tai Chi Exercise" versus a standard program of "Western Exercise" consisting of endurance, strength, and flexibility training in community-living women and men age 70 years and older. The primary endpoints of the study are changes in physical functioning associated with a lower risk of falling, psychological status and health-related quality of life as measured by standard self-report questionnaires, and autonomic tone as measured, by baroreflex sensitivity. Women and men living in the communities of Menlo Park, Palo Alto, Mountain View, and Sunnyvale, CA who are ambulatory and without life threatening diseases will be recruited, perform a baseline evaluation, and if found eligible, will be randomized to one of three groups: Tai Chi Exercise, Western Exercise, or no-exercise 'attention' control. A total of 210 subjects will be randomized with a target of 180 subjects completing the one year study (60 per group). The two treatment conditions will consist of class and at-home sessions. Throughout the year, classes of 45-minutes will be held twice a week. On all days that classes are not held, subjects will be instructed to perform their assigned exercise program for 20-30 minutes. Follow-up evaluations will be performed at three, six and twelve months, with primary outcomes being assessed at twelve months. The results of this research will provide the first direct comparison of Tai Chi versus Western Exercise in this high priority target population and will help identify interventions for maintaining independence and enhancing